Patent GB-908050-A (GB)
Title: An improved apparatus for testing liquid samples
Inventor: COLLINS GEOFFREY CHARLES
IPC: A61B5/145
Filed: 1959-08-10
Abstract: 908,050. Testing liquid samples. EVANS ELECTROSELENIUM Ltd. July 21, 1960 [Aug. 10, 1959], No. 27239/59. Class 40 (3). An instrument for measuring the time interval between the application of a given treatment to a liquid test sample and the consequent clotting of the sample comprises means for passing a beam of light through the liquid test sample to a photo-electric device controlling the energization of an electricity motor, a counting or timing device which is started simultaneously with the application of said treatment, and means for automatically stopping the counting device when the energization of the meter changes to a given stopping value owing to a reduction of the light reaching the photo-electric device consequent upon the clotting of the test sample. Circuit arrangement.-The major part of the apparatus is duplicated to carry out the test on separate samples in test tubes TT1, TT2, illuminated by a common light source L3 and associated with photo-cells PC1, PC2 connected through potentiometers VR1, VR2 to milliammeters M1, M2. The closure of a mains switch SW3 energizes transformers T1, T2 which illuminate lamp L3, lamps L1, L2 associated with the milliammeters M1, M2 and photo diodes D1 and D2, and also apply voltages to rectifier networks BT1, RT2 connected respectively to lines 1, 2 and through an intermittently operated switch SW6 to lines 3, 4. Initially with switches SW1, SW3 closed the cell PC 1 is illuminated and light also passes from the source L1 to photo-diode D1 so that windings RA1, RB1 of relay R1 are energized, and contact RC1 is opened. The relay R1 (or R2) is such that windings RA1, RB1 tend respectively to open and close contact RC1, but with both windings energized, the contact remains in the position previously taken up. The potentiometer VR1 is adjusted so that the pointer of the milliammeter is at zero, when the cell RC1 is illuminated by source L3. The reagent is now added to the test sample and switch SW1 opened so that winding RB1 closes contact RC1 which connects a timing device CT1 to lines 3, 4 and a switch SW6 intermittently closed at regular intervals, e.g. 1 second, by a synchronous motor (not shown). The test tube TT1 is now positioned and the pointer is adjusted by potentiometer VR1 to a position in which it does not obstruct the light falling on the diode D1 and the switch SW1 is again closed, but contact RC1 remains closed so that the timing member CT1 is operated by switch SW6. When the clotting has increased the turbidity of the sample so that the pointer of the meter M1 has reached a prescribed value, a vane on the pointer prevents light from source L1 from reaching diode D1 so that the winding RA1 is now operative to open contact RC1 and the counting or timing operation is discontinued. Heaters H1, H2 controlled by a switch SW4 and a thermostatic switch SW5 maintain the samples in the tubes TT1, TT2 at a predetermined temperature. Details of instrument assembly.-A casing 5 has a front wall 6 and a sloping wall 8 with a downward extension 9 having a horizontal portion 10 connected to a rear wall 7. A cover 13 forms an upper compartment 14 in which blocks 20, 21 mounted on the base 10 have sockets 18, 19 for the test tubes, and intersecting horizontal holes 23, 24 for the passage of light from the lamp L3 to the photo-cells PC1, PC2 via lenses such as 25, 26, 27 for the cell PC1. A lower compartment 17 houses the rectifier networks RT1, RT2 and the timing switch SW6 operated by a cam 45 rotated by a synchronous motor 44. A casing 31 supported on the sloping wall 8 by a flanged cover 30 has a base-plate 29 carrying blocks 32, 33 with recesses for the photo diodes D1, D2 and each having an aperture such as 34 for block 32, in register with the respective light sources L1, L2. The milliammeters M1, M2 are secured to the base-plate 29, and the pointer of each instrument has a vane 39 which cuts off the light from the source L1 or L2 to the associated diode D1 or D2 when the meter registers a predetermined value. The switches SW1 and SW2, potentiometer controls 42 and counting mechanisms CT1, CT2 are located in the sloping wall 8, and lamps L4, L5, together with the switches SW3, SW4 are mounted in the front wall 6. The heater elements H1, H2 and the thermostatically controlled switch SW5 are located adjacent the blocks 20, 21 in the compartment 14.